1. Technical Field
Generally, the invention relates to high pressure fluid cutting systems. Particularly, the invention relates to high velocity cutting nozzles for connection to the fluid supply tube of high pressure fluid cutting systems. Specifically, the invention relates to cutting nozzles comprising a housing which threadably connects to the fluid supply tube for receiving pressurized liquid therefrom spraying outwardly through a spray outlet bore of the housing.
2. Background Information
High pressure liquid cutting devices are commonly used for cutting various sheet materials such as plastics, and masonry materials such as brick and concrete slabs. Such cutting devices are also used for drilling and abrading materials. High pressure liquid is also often used to clean materials such as brick and masonary. Such cutting devices usually include an electric motor which drives a hydraulic pump supplying a working fluid to a high pressure intensifier unit. The intensifier draws a cutting liquid in the form of water from a reservoir, and discharges the water at a very high pressure (e.g. 20,000 to 70,000 psi or more) through the fluid supply tube to the cutting nozzle to produce a fluid jet to cut through the desired material. The fluid jet may range in diameter from about a thousandth of an inch up to about fifteen thousandths of an inch or more, at a velocity of about 1,000 to 3,000 feet per second.
Many prior art cutting nozzles are prone to prematurely wearing out due to abrasion caused by the high pressure and velocity of the water traveling through the nozzles upstream of the orifice. Turbulence upstream of the orifice also causes lack of cohesiveness of the fluid jet. That is, convergence of the various velocity vectors of the fluid within the fluid jet at the orifice only extends for a short distance upon exiting the orifice. This results in a more dispersed fluid jet having less cutting force so only shallower cuts may be made, a wider width of cut or kerf, and more overspraying or wetting of the material adjacent the cut. Conversely, a more cohesive fluid jet provides a finer fluid jet, more precise cutting, and deeper cuts.
One attempt to reduce such turbulence is the a liquid jet cutting device and method disclosed in U.S. Pat. No. 3,997,111 issued to Thomas et al. on Dec. 14, 1976. The disclosed device includes a source of high pressure fluid, a jet nozzle, and a high pressure conduit connecting the fluid source to the nozzle. A liquid collimating device is disposed directly upstream of the nozzle comprising a housing interconnected between the conduit and the nozzle. The housing defines a flow collimating chamber directly upstream of the nozzle through which the high pressure liquid is delivered to the nozzle. The cross-sectional area of the flow collimating chamber must be at least greater than one hundred times the cross-sectional area of the nozzle opening. The liquid jet produced is claimed to have relatively little dispersion and a relatively narrow kerf.
An orifice assembly and method providing highly cohesive fluid jet is disclosed in U.S. Pat. No. 5,226,597 issued to Ursic on Jul. 13, 1993. The orifice assembly includes a housing that receives pressurized fluid from a supply tube. The housing has a passageway therein through which the fluid flows. The passageway has an orifice element therein having an orifice for producing the fluid jet, and a converging section disposed upstream of the orifice that extends toward the orifice element. The converging section is designed to reduce turbulence upstream of the orifice and thus produce a more cohesive fluid jet emitted from the orifice. A section having a rounded surface is disposed between the converging section and the orifice element which joins the converging section and an upstream portion of the orifice element. The section is designed to further improve the cohesiveness of the fluid jet by further reducing turbulence upstream of the orifice.
Although these devices are adequate for the purpose for which they were intended, the first device has additional length and adds weight to the cutting assembly. Additionally, neither device directly addresses the problem of nozzle wear.
Therefore, the need exists for an improved high velocity cutting nozzle that reduces turbulence upstream of the orifice to produce a narrow kerf, and that has a significantly longer service life prior to wearing out.
Objectives of the invention include providing a high pressure nozzle which has reduced turbulence to produce a finer kerf.
Another objective of the invention is to provide such a cutting nozzle with significantly reduced internal wear due to abrasion of the water flow providing a longer service life, and which solves problems and satisfies needs existing in the art.
These objectives and advantages are obtained by the improved high velocity cutting nozzle for connection to a fluid supply tube of a high pressure fluid cutting system of the present invention, the general nature of which may be stated as including: a housing adapted for connection to the fluid supply tube having a flow-directing bore for receiving a liquid from the fluid supply tube and extending partially through the housing, the flow directing bore including a convergent inlet portion having an annular inner surface for reducing turbulence in the flow-directing bore, and a bulbous outlet portion having an annular curved divergent surface and an annular curved convergent surface, and a spray outlet bore extending inwardly from a front surface of the housing in fluid communication with the bulbous outlet portion of the flow-directing bore through which the liquid is directed as a high velocity liquid cutting jet; and an orifice plate disposed within the housing in co-axial fluid communication with the flow-directing bore and the spray outlet bore immediately downstream of the flow-directing bore, the orifice plate having an orifice of a diameter that is smaller than a minimum diameter of the flow-directing bore for producing a high velocity fluid jet.
According to another aspect, the objectives and advantages are obtained by the improved method for extending the service life of a high velocity cutting nozzle, the general nature of which may be stated as including the steps of: producing a flow of high pressure fluid; passing the flow through a flow-directing bore including a convergent inlet portion having an annular inner surface, and through a bulbous outlet portion having an annular curved divergent surface and an annular curved convergent surface; and passing the flow through an orifice closely adjacent the flow-directing bore having an orifice of a diameter that is smaller than a minimum diameter of the flow-directing bore for producing a high velocity fluid jet.